Friday, July 12, 2019

Noxious weed look alikes – don’t pull the wrong plant!

by Irene Shonle
It is heartening to see so many people being committed stewards of their land who are working to eradicate the noxious weeds on their property.  Thank you to everyone who is participating!  A word of caution -  it is possible to be a little too enthusiastic. This happens when someone pulls or treats the wrong plant – a plant that has the misfortune of looking like a noxious weed. These look-alike plants are often native, and can provide good habitat for pollinators, or at the very least, will occupy space that otherwise could be invaded by a noxious weed, so it’s best to learn how to distinguish which is which.

Some of the most common mistaken identities up here are:

  • Golden banner/yellow toadflax,
  • Pineapple weed/scentless chamomile,
  • Cutleaf daisy/oxeye daisy 
  • Fireweed/purple loosestrife.

Golden banner is a native plant – it blooms in the spring, and has solid yellow flowers, and three-lobed (trifoliate) leaves. Yellow toadflax blooms in the second half of summer with two-tone yellow flowers with a darker throat, and has strap-shaped leaves.
Golden banner

Yellow toadflax
Pineapple weed, while an introduced plant, is not on the noxious weed list. It is, however, having a very good year, and can be easily controlled by hoeing or pulling.  It has ferny leaves that, when crushed, smell like pineapple. The whole plant only gets to 6-8” tall at the most. It develops small yellow buttons, but never white ‘petals’ (ray flowers). Scentless chamomile also has ferny leaves, but they have no odor (the plant names give good ID clues). It gets up to 3’ tall, and has hundreds of white flowers.
Pineapple weed
Scentless chamomile
Cutleaf daisy is a native plant with small white flowers and finely cut leaves that could look a little ferny. It can (and has been) mistaken for pineapple weed, scentless chamomile and oxeye daisy. The flowers on the native bloom in the spring, and the foliage has no smell. The whole plant is no taller than about 4” tall. Oxeye daisy blooms mid-summer, and has much larger flowers, as well as broader leaves with teeth (not ferny). The plant grows 1’-3’ tall.
Cut-leaf daisy and penstemon
Oxeye daisy
Fireweed is a native plant with 4 pink petals. It blooms mid-summer to fall. The leaves are alternate, and the plant can grow up to 4’ tall. Purple loosestrife is not known to be up at this elevation, but people have frequently pulled out fireweed by mistake. Loosestrife has opposite leaves (or even whorled – meaning that four leaves come out of the stalk at the same place). It has 5-7 purple petals and can grow up to 8’ tall. 

Finally, we have many wonderful native thistles, and it’s easier to just learn to recognize our two common noxious thistles, Canada thistle and musk thistle, rather than all of the native thistles. Musk thistle has large, solitary purple flowers with a formidable row of teeth under the flower. The leaves have a whitish edge. Canada thistle usually forms thickets due to the root system, and has clusters of small purple flowers.  See below table for a quick reference to distinguishing these plants.

Native plant
Noxious weed
Golden Banner
Solid yellow, spring
Yellow toadflax
Two-toned with a darker throat, Mid-late summer
(Pineapple weed – not native, but not noxious)
Just a yellow button, spring-mid summer
Ferny, smells of pineapple
Scentless chamomile
White flowers, Mid-late summer
Ferny, odorless
Cutleaf daisy
Small white flower, spring
Finely cut, a little ferny
Oxeye daisy
Large, white, blooms
Small teeth on leaves
4-petals, pink, mid-late summer
Alternate leaves
Purple loosestrife
5-7 pink petals, mid-late summer
Square stem, 4 or more leaves come out of same place on stalk (whorled)
Native thistles
Varies – white, pink, brownish
Varies – usually very white on underside
Noxious thistles (especially Canada and Musk)

For more information on thistles, see this brochure:

Irene Shonle is the CSU Extension Agent and Director in Gilpin County

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